An extension of ongoing research on basic cognitive processes in retarded and normal children is proposed. The information from the basic research component will be applied to the development of a cognitive preschool screening test for the early detection of mild mental retardation and learning disabilities. Despite the proliferation of screening tests designed for the preschool aged child, early reliable identification has been achieved only for the more severe forms of mental retardation. The largest number of children classified as mentally retarded fall in the mild range. Identification of these children typically does not occur until the child has echibited repeated failure in the school setting. Such failure often compounds the child's intellectual deficiencies with behavioral and attitudinal problems that make remediation difficult. The project extends ongoing research on basic cognitive processes in young children. A variety of cognitive tasks which cumulatively require a broad range of processing skills will be investigated in three-through nine-year-olds. The sample will consist of normal preschool children as well as grade school students who are classified as a) normally achieving, b) mildly retarded, or c) learning disabled and will provide a broad range of chronological age, mental age and intellectual level. This will allow for the assessment of the relationship between these three parameters and the multiple cognitive processing skills present at different stages of development across the sample. Similarities and differences will be explored between the mildly retarded and learning disabled students who share the common experience of school failure although only one of them presents with an intellectual deficiency. Based on these data, a preschool screening test will be constructed and its concurrent validity assessed.